h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Poetic licence?

Yes.

Effers, are you aware that *all* the planets have elliptical orbits? It´s a feature of gravitational attraction, rather than anything wrong with Earth.

Yes of course Xan. Do you think I'm thick or something?

**

Because its elliptical I realised that that relates to the 'Quickening'. It's an old term used when it suddenly becomes apparent the daylength is increasing...sometime in February in the northern hemisphere.

And Spring can really start to spring.

For the first few weeks after the winter solstice...it all a bit of a 'no show' like now.

I'm constantly amazed that the ancients were able to tell when it was the solstice with great reliability, in the complete absence of mechanical clocks.

Mechanical clocks - were they that good?

The ancients probably counted days from the equinox.

The ancients probably used things called Knowledge and Observation.

Knowledge and Observation is all very well. But when your tools are sticks and stones, how do you know or observe that today was five seconds longer than yesterday?

That's the order of magnitude of the difference we're talking about.

The solstice this winter was on December 22nd. Nine days later the day had only lengthened by one minute. What amazes me is that people without access to mechanical clocks could tell pretty accurately when it was solstice (or equinox, for that matter), year after year.

(Note: figures given in previous post are applicable to the latitude at which I'm sitting, almost 54 degrees north. The rate at which the length of your day changes will vary.)

Didn't they use really BIG stones in some places?

Well, the thing is they didn't have stuff like mechanical clocks and calendars getting in the way.

The time of day (or night) and the time of year can be accurately worked out by the position of the sun, the moon and the stars.

Mechanical clocks and calendars present us with a completely man-made notion of the passage of time and how it's divided up. I put it to you that these things are actually a hinderance rather than a help when it comes to being able to accurately estimate things like solstices and whatnot without assistance.

"The time of day (or night) and the time of year can be accurately worked out by the position of the sun, the moon and the stars"

Oh yeah?

How, exactly?

Serious question: if I put you on a desert island, how would you go about working out what date it was? It's all very well saying "the position of the sun moon and stars", but how do you actually MEASURE that, lacking clocks, verniers and similar relatively modern gadgets?

(I mean... I *know*... I just find it amazing that people actually worked it out. History is full of unsung geniuses.)

<(I mean... I *know*... I just find it amazing that people actually worked it out. History is full of unsung geniuses.)>

Like Eratosthenes: http://www.youtube.com/watch?v=G8cbIWMv0rI

"Eratosthenes' only tools were sticks, eyes, feet and brains, plus a zest for experiment."

Hmm. Eratosthenes is someone I'd have said was pretty much the definition of a sung genius. He's been dead for thousands of years, and yet we've both heard of him.

I'm thinking of the people we've none of us heard of, the people who educated the people who designed Stonehenge, say.

Shadows when the sun is overhead provide a lot of clues regarding seasonality, as does the precise points on the horizon that the sun, moon, and stars rise and fall each day. The "ancients" would have had dedicated men (and women?) who specialised in knowledge of the heavens and would link that knowledge to the seasons and various festivals linked to food production cycles.

Yes, I was going to mention that he was pretty well sung. Nevertheless, he needed no mechanical devices to produce quite accurate results.

Re: post 35 ... Now there is a job that I would have enjoyed. Study sunrises and sunsets and other incidentals, and have the 'expenses' of life in the day met by the rest of the community. Oh wait, isn't that sort of like Welfare?

Stone monuments like Maesehowe and the Brodgar rings on Orkney, very precisely tell you when a specific day has arrived. In the case of maesehowe, the sun will *only* make it through the narrow entrance passage, all the way to the back wall on one day. Of course nowadays, due to the earth's procession, that time has changed, but certainly you can note the exact position of a shadow on one particular day, and be certain that the shadow will only be in that position again at the same time next year.

There's even a maeshowe-cam to demonstrate the fact! http://www.maeshowe.co.uk/

If I knew I was likely to stuck on a desert island for at least a year, and i decided that I still wanted to keep a track of time (unlikely I reckon, but anyway..), I would pretty much do the same thing, but on a smaller scale. I'd find a nice big stone that gets the sun all year round, and start marking daily/hourly positions with chalk or some other marking stone on a nearby slab. I reckon, however to know precisely, the length of an hour or day, you would probably have to do this religiously for one year till the shadow's edge returns to point A. You'd then have your baseline and could then sub-divide markings.

I reckon you'd need someone else on your island with you to do the mundane stuff like hunting, cooking, etc for at least a year though...